The Human PoWeR Laboratory Physiology ofof Wearable Robotics Dr. Gregory S. Sawicki
MECHANICS ENERGETICS NEURAL CONTROL Lower-limb Joints Muscle-Tendon Units Muscles Whole-Body
Carbon fiber shank Polypropylene foot Artificial Pneumatic Muscle Load Cell Compressed air via nylon tubing Steel hinge joint Moment arm ~10 cm Bilateral Powered Ankle Exoskeletons Total Mass ~ 1.1 kg < 5% M body
Proportional Myoelectric Control Powered Ankle Exoskeleton with Artificial Muscle SOL EMG Computer Interface Plantar Control Signal Pressure Regulator
Uphill: 15% 1.25 m/s Powered Walking: O 2 Consumption
Energy Savings: Powered Assistance Net Metabolic Power (W/kg) Unpowered Powered -13% * -11% * -12% * -10% * Surface Gradient (%) Sawicki, Ferris J Exp Biol (2009b) 1.25 m/s 9 SUBJECTS
Push-Button Control Push ButtonControl Signal Pressure Regulators Computer Interface Therapist Control A. Therapist Control Patient Control B. Patient Control Sawicki et al. JNER (2006).
In Vitro Muscle-Tendon Work Loops Specified Muscle Stimulation Timing Specified Muscle-Tendon Length Trajectory Signal Generator Length Stim Muscle-Tendon (MT) Frog Plantaris Muscle Fibers (CE ) Achilles’ Tendon (SEE) Electrical Stim Muscle Stimulation Amplitude, Duration Sonomicrometer CE Length MT Length Muscle Ergometer Muscle Force
Protocol: Activation Onset Phase % 250 ms (4 Hz) % Muscle-Tendon Length Trajectory (mm) + Lengthening - Shortening -12.5% +12.5% +25.0% +37.5% +50.0% 100 ms 40% duty
Muscle-Tendon Force and Length N=6 Cycle (%) Stimulation Period Muscle (CE) Δ Length (mm) Force (N/g) Tendon (SEE) Δ Length (mm) ms
Imaging: Manipulate Muscle-Tendon force with Parallel Elastic Ankle Exoskeleton Parallel Elastic Exoskeleton + Rotating Platform Force Platform 1. External Forces 2. Joint Kinematics Ultrasound Probe Muscle-Tendon Junction Position 3. Muscle + Tendon Lengths 4. Electromyography 5. Metabolic Cost In Vivo Muscle-Tendon
MUSCLE ERGOMETER SONOMICROMETER ELECTRICAL STIMULATOR or PNEUMATIC VALVES BIOLOGICAL MUSCLE-TENDON or ARTIFICIAL MUSCLE-TENDON Feedback Control: VIRTUAL BODY DYNAMICS Muscle-Tendon Length Change Muscle-Tendon Force VIRTUAL NERVOUS SYSTEM Feedforward + Feedback Muscle Activation Muscle Length and Velocity (i.e. Ia, II) (i.e. Ib) In Vitro Muscle-Tendon
Design: Sawicki et al. JNER (2009). Wearable Robots and Elastic Actuators